Family Proscylliidae:

Finback Catsharks — 5 species &

Family Pseudotriakidae:

False Catsharks — 4 species

Closely related to the scyliorhinids are the finback catsharks
(Proscylliidae),
which includes the smallest carcharhinoid: the Pygmy Ribbontail Catshark (Eridacnis
radcliffei); this species matures at about 6 to 7.5 inches (15 to 19 centimetres),
rivaling the smallest squaloids in size. In addition to its small size at
maturity, this species is remarkable for the large size of its pups compare to
with their mother: a 7-inch (18-centimetre) female might give birth to one
or even two 4.3-inch (11-centimetre) pups. It is possible that female
Pygmy Ribbontails grow considerable when pregnant as only the larger females
contain near- or full-tem fetuses, while small females contain only
embryos.

The False Catshark (Pseudotriakis microdon) is a rare, deep-sea species,
generally inhabiting abyssal slopes at depths between 660 and 4,900 feet (200
and 1,500 metres). Growing to a length of about 10 feet (3 metres), this
little-known shark is among the largest of carcharhinoids.. The False Catshark
is rather slender in overall body form, characterized by a long, low first
dorsal fin, long narrow eyes (seemingly frozen in a permanant 'squint'), and
long, teardrop-shaped spiracles. The huge, oily liver, mush musculature, soft
fins and skin of the False Catshark suggest that it is relatively inactive and
sluggish. Due to its many odd features, this species was
long considered to be the sole member of the family Pseudotriakidae, but new
evidence suggests that it is closely related to the Slender Smoothhound (Gollum
attenuatus — the only shark named after a character in Tolkein's Lord of the
Rings trilogy), which is therefore also placed in that family. Recent work by
ichthyologist Kazunari Yano off Okinawa, Japan, and Three Kings Ridge off New
Zealand, has revealed a few secrets about this animal's reproductive biology.
Males of this species mature at a length of about 8 feet (2.4 metres), while
females mature at a length of about 9 feet (2.8 metres). Gestation period in the
False Catshark remains unknown, but two pups
are typically born per litter, each about 2.5 feet (75 centimetres) long. For
decades it had been known that adult female False Catsharks produce an
astonishing number of eggs — some 20,000 in one ovary of a 9-foot specimen from
the western Indian Ocean. Thanks to Yano's work, we now know that these eggs are
used as an accessory food source for False Catshark pups to fuel late stages of
their development. Although intrauterine oophagy (egg-eating) occurs in most
— possibly all — mackerel sharks (order Lamniformes), the False Catshark provides
one of only two known cases of this form of fetal nutrition in a non-lamnoid
shark (the other case is the Tawny Nurse Shark [Nebrius ferrugineus], an
orectoloboid).

The
False Catshark (Pseudotriakis microdon) is a rare, little-known abyssal
species that goes about its fishy business largely ignored by humans rushing
about their own clamorous world far above. In a 1992 paper by ichthyologists
Kazunari Yano and John Musick, clear and ominous differences in the diets of
False Catsharks from the Pacific versus those from the Atlantic were noted.
Specimens from off Okinawa, Japan, and Three Kings Ridge, off New Zealand,
indicated that in the north and south Pacific this shark feeds on cut-throat
eels, grenadiers, snake mackerel, lanternsharks (family Etmopteridae), squids
and octopuses. Surprisingly, stomach contents of False Catsharks from the deep
Pacific also included some oceanic surface-dwelling fishes, such as frigate
mackerel, needlefishes, and even two pufferfishes usually associated with
floating mats of sargassum weed; since these fishes almost certainly do not
venture far from the surface, the authors concluded that they were probably
scavenged after their corpses sank to the bottom. A specimen from the Canary
Islands, in the northeastern Atlantic, indicated a far less pristine dining
environment: its stomach contained mostly man-made garbage, including potatoes,
a pear, a plastic bag, and a soft drink can manufactured in Lisbon. It seems
that, even tucked away in the Stygian depths of the deep-sea, the False Catshark
is not beyond the reach of human impact.